Businesses or other entities having a need for volume printing typically purchase a production printer. A production printer is a high-speed printer used for volume printing (e.g., one hundred pages per minute or more). Production printers are typically continuous-form printers that print on webs of print media that are stored on large rolls.
A production printer typically includes a localized print controller that controls the overall operation of the printing system, and a marking engine (sometimes referred to as an “imaging engine” or as a “print engine”). The marking engine includes one or more printhead assemblies, with each assembly including a printhead controller and a printhead (or array of printheads). An individual printhead includes multiple tiny nozzles (e.g., 360 nozzles per printhead depending on resolution) that are operable to discharge ink as controlled by the printhead controller. A printhead array is formed from multiple printheads that are spaced in series across the width of the print media.
When in operation, the web of print media is quickly passed underneath the printhead arrays while the nozzles of the printheads discharge ink at intervals to form pixels on the web. In order to ensure optimal print quality, a print quality chart can be printed in a pattern that exposes any print irregularities caused by clogged nozzles or misalignment. In cyan, magenta, yellow, and black (CMYK) printing systems, a cyan, magenta or black nozzle defect will be apparent on a printed diagnostic chart since their output contrasts with the paper medium. However, it is difficult to detect problems in nozzles that apply yellow or clear fluids to a medium.